During the inflammatory process T cell transmigration through the endothelial cell layer and migration into the underlying and surrounding extracellular matrix is initiated by T cell adhesion to the endothelium. T cell - endothelial cell adhesion is mediated by specific ligands resident on the surfaces of both the T cell and the endothelial cell, specifically, VLA-4 (a4beta1) on the T cell and VCAM-1 on the endothelial cell. We have demonstrated that engagement of this ligand pair evokes changes in 72 kDa gelatinase as well as plasminogen activator and plasminogen activator inhibitor-1 in both cell populations, consistent with the manifestation of an invasive phenotype in the adherent T cell population and an "activated" phenotype in the endothelial cells. Resultant proteolysis of basement membrane and interstitial matrix components is thought to facilitate T cell extravasation out of the affected vessel and toward the site of inflammation. In this proposal wee will identify and characterize selected adhesion-inducible T cell and endothelial cell proteinase/proteinase inhibitor systems and T cell surface adhesion molecule expression. We will investigate and identify the signal transduction systems triggered by engagement of the VLA-4/VCAM-1 ligand pair in these two cell types. This will be accomplished utilizing an in vitro culture model utilizing cloned murine T cell clones specific for myelin basic protein and selected human T cell clones isolated from multiple sclerosis patients; an in vivo adoptive transfer murine model for experimental allergic encephalomyelitis (EAE) and a SCID mouse containing grafted human skin and reconstituted with human peripheral lymphocytes. A variety of methodologies will be employed including cell culture, zymography, reverse zymography, gene products, histology, immunohistochemistry and an animal model of EAE. These experiments will lead to a better understanding of T cell migration through and interaction with local extracellular matrix and the development of new and novel therapies directed at modulating selected proteinase/proteinase inhibitor cascade systems in the inflammatory processes of arthritis, vasculitis, organ rejection.